Load Boards are custom-made printed circuit boards (PCB) that act as an interface between automated test equipment (ATE) and a device under test (DUT). The load board provides an electrical and mechanical interface between the ATE and DUT. Generally, a load board includes one or more sockets for the DUT, interface pads for the ATE, and electrical components (e.g., resisters, capacitors, inductors, etc.) needed for the DUT. In some instances, the DUT may be soldered to the load board.
LEDs undergoing reliability stress tests are frequently soldered to load boards that connect the LEDS in series or parallel circuits so that they may be driven from a common power source. During LED testing the load board serves as a heat transfer medium. Excessive heat from the LED junction is transferred by conduction to a heatsink or temperature control platform under the load board. To maximize heat transfer, the load board is firmly clamped by a clamping mechanism to the temperature control platform, thereby minimizing any air gaps that may slow heat transfer. This may be done with regularly placed screws, lever clamps, or other means. Many of these means rely upon a few discrete, common contact points. Pressure applied at these common points is then distributed by the load board to the structure of the load board itself.
However, the best materials for load boards are soft metals such as aluminum and copper. These materials may easily deform under point loads, resulting in a non-uniform clamping force. In some instances, air gaps may form. To mitigate this problem, load board clamping mechanisms have been designed with highly distributed pressure points, created using spring-loaded electrical connectors called pogo pins. Although each pogo pin does not apply much force, the pogo pins are small and many can be positioned in a regular array to produce a uniform clamping force. Additionally, because the pogo pins are conductive, they may serve as electrical contacts for the load board, thereby eliminating the need for a connector.
Although pogo pin arrays effectively distribute the clamping force, each array must be custom built to exactly fit the load board's corresponding LED pattern. Accordingly, each LED board type requires designing a different clamp to implement the correct array. As most laboratories utilize dozens of different load board types, this method is expensive and cumbersome.